Recent studies have shown that a number of nuclear oncogenes, including fos, encode nuclear proteins that function as trans-acting transcriptional factors. Previous studies showed that expression of a mutant v-fos protein or overexpression of the c-fos proto-oncogene can both lead to cell transformation. Controlled expression of the c-fos protein however, does not lead to malignancy. It is thus likely that only a small subset of all the genes sensitive to regulation by Fos oncogenes actually contribute to induction of a transformed phenotype. This proposal outlines experiments designed to identify and study the regulation of genes whose expression is altered specifically in response to transformation of cells by the Fos oncogenes. A comparison of gene expression in v-fos transformation cells and in revertant clones isolated from the former has already lead to the identification of such genes. These genes encode alpha1 (I) and alpha2 (I) procollagen, two major glycoproteins whose expression is inhibited in Fos transformed cells, but not in revertant cell lines that produce comparable levels of the Fos protein. cDNA libraries enriched for genes whose expression is altered by Fos transformation will be prepared by subtractive hybridization between mRNA's expressed in the transformed cells and the revertants. These libraries will be used to clone additional genes whose altered expression either negative or positive is specifically associated with Fos-induced transformation. Once isolated, the cis-acting regulatory regions that control the transcription of these genes will be identified and defined. These regulatory sequences will then be used to purify the transacting factors which interact with these sequences to alter gene expression. Once purified, the proteins will be sequenced and oligonucleotide probes developed to molecularly clone and characterize the corresponding genes. These studies will thus provide insight into the aberrent mechanisms of gene regulation associated with Fos induced cell transformation.